Movable shroud for variable jet engine exhaust nozzles



Feb. 7, 1961 R. F. DREIFKE MOVABLE SHROUD FOR VARIABLE JET ENGINE EXHAUST NOZZLES Filed Aug. l1, 1952 3 Sheets-Sheet l R. F. DREIFKE Feb. 7, 1961 I MOVABLE SHROUD FOR VARIABLE JET ENGINE EXHAUST NOZZLES Filed Aug. l1, 1952 5 Sheets-Sheet 2 INVENTOR RAYMOND FRANK DRI-:l FKE BY QM fir/wwf/f n Feb. 7, 1961 R. F. DREIFKE MOVABLE SHROUD FOR VARIABLE JET ENGINE EXHAUST NOZZLES Filed Aug. ll, 1952 5 Sheets-Sheet 5 nite MOVABLE SHROUD FOR VARIABLE JET ENGINE EXHAUSI` N OZZLES Raymond F. Dreifke, St. Louis, Mo., assignor, by mesne assignments, to Westinghouse Electric Corporation, a corporation of Pennsylvania Filed Aug. 11, 1952, Ser. No. 303,775

7 Claims. (Cl. 60-35.6)

annular cooling of air duct surrounding the combustion.

chamber and exhaust nozzle of the afterburner designed to induce the flow of cooling air and preventing disastrous overheating. Flow of cooling air is obtained in part by providing a cowling opening to build up ram pressure upon forward ight, and in part by utilization of the augmentation or ejector eifect of the exhaust gases. Augmentation of the flow of cooling air is accomplished by proper positioning of the rear opening of the shroud with respect to the exhaust nozzle, so that the blast of gases from the exhaust nozzle will exert a suction upon and accelerate the ilow of the ducted cooling air at the rear opening of the shroud.

While the design of such a shroud is not diicult in the case of a simple jet engine Without an afterburner, it is much more difficult where afterburning is employed. Factors causing such diticulty are the increased range of cooling requirements and the change in the pattern of blast gases emerging from the exhaust nozzle, such pattern being hereafter referred toas the blast cone.

The problem is further complicated when a variable diameter discharge nozzle is utilized. The rear end opening of the shroud must be removed from the blast cone during both afterburning and non-afterburning operation. Yet, if an afterburner has a fixed end opening of Sullicient diameter to provide clearance for the blast cone when the variable nozzle is in open, or atterburning, position, such opening will be undesirably large for nonafterburning operations causing increased aerodynamic drag of the total nacelle. The drag resulting from the excess of shroud opening over nozzle diameter is referred to as the base drag of the nacelle or shroud. Additionally, on increase in the size of the exit nozzle during afterburning operations there should be no de.

crease, but preferably an increase, in the ejector cooling.

Accordingly, it is a principal object of the present invention to provide a variable shroud adapted to form a well-streamlined nacelle afterbody having minimum base drag under all conditions of operation of the jet engine and afterburner.

l It isv a further object of the present invention -to provide an afterburner cooling shroud characterized by a variable diameter end opening for clearance of the blast cone under both afterburning and non-afterburning conditions of operation.

States Patent C 2` to adapt it for e'cient operation in non-afterburning position.

A still further object of the present invention is to interrelate the operation of a variable shroud with that of a variable diameter exhaust nozzle, so that they simultaneously assume their optimum relatonshps'for afterburning operation or for non-afterburning operation.

With the above and other objects in view, my invention resides in the novel features of form, construction, arrangement, and combination of parts presently described and pointed out in the claims.

In the accompanying drawings (three sheets)- Fig. 1 is a side elevation of a variable shroud embodying the present invention and shown in atterburning position, with the non-afterburning position indicated by phantom lines;

Fig. 2 is an enlarged sectional view taken along line 2 2 of Fig. l showing the afterburner nozzle, shroud and shroud extender structure in afterburning position;

Fig. 3 is a view similar to Fig. 2 showing the component parts in non-afterburning position;

Fig. 4 is a fragmentary rear end view of the nozzle and shroud extender structure shown in position corresponding to Fig. 3;

Fig. 5 is a sectional view taken along line 5-5 of Fig. 3;

Fig. 6 is a fragmentary view partly in section taken along line 6-6 of Fig. 5;

Fig. 7 is a sectional view taken along line 7--7 of Fig. 1. v

Referring now to the drawings by reference numerals and in greater detail, there is attached to the aft end of a jet engine, not shown, an afterburner support ring 1 by which is secured to the jet engine the afterburner combustion chamber designated 2, having a tapering throat portion 3, a generally cylindrical portion 4, and a tapering exit portion 5, as shown in Fig. 3. W'thin the combustion chamber throat portion 3 are to be installed the conventional afterburner elements including fuel nozzles and lines, dame-holdingv apparatus, etc., such as are familiarly used in afterburner construction.

Mounted to the aft end of the Aexit portion Stof the afterburner combustion chamber 2 isa variablediameter discharge nozzle 6 (Figs. 2- and 3), which comprises a hinge ring 7 spot-welded around the aft end of said exit portion 5, and an annulus made up of a plurality of T-shaped nozzle segments 8, each having a lipY 9rat its forward end for hinging engagement in the hinge ring 7,. The T-shaped nozzle segments 8 being arranged in sideby-side relationship, each'hasa joggled overlapping portion 10 (Figs. 4 and 5) along one side vthereof for oyerlapping the adjacent T-shaped segment 8. The stem portions 11 of said T-shaped segments k8 are arranged radially outward from the central longitudinal axis, not shown, of the combustion chamber; and Vsaid stern portions 11 taper in depth increasingly fromthe lip. 9 aft to a section of maximum depth 12 approximately midway along the length of theY said nozzle segments 8. In the section of maximum depth 12 and adjacentthe outer edge thereof, each stem portion 11 has a transverse bore 13 (Fig. 5) for attachment to the shroud extender struc'- ture, which will be hereafter described.

Referring nowY to Fig. 7,` there are spotlwelded at circumferentially spaced intervals around the cylindrical It is an additional object of the present invent'on to provide an afterburner shroud having provision for adequate ejector cooling when operated in conjunction with a variable diameter exhaust nozzle.

A further object is to provide a streamlined shroud extender structure, including elements extensible convergingly from the aft end opening of a xed shroud,

portion 4 of the afterburner combustion chamber, a plurality of forward spacer channels 14 andaft spacer channels 1S, the outer surfaces of which are bearing surfaces, designated 16 and 17, respectively. The bearing surfaces 16 and 17 slidingly support, and 'space outward from said afterburner combustion chamber 2, the cylin# drical inner wall 18 of a shroud generally designated 19. The shroud 19 has a cylindrical outer shroud wall 20, and a streamlined aft portion 21 which curves convergingly from the cylindrical outer shroud wall 2t) to an aft end opening 22 of somewhat greater diameter than the hinge ring 7 (Figs. 2 and 3).

The inner cylindrical wall 18 of the shroud 19 is spaced from and held rigidly to the outer cylindrical shroud wall 20 byra plurality of spot-Welded overlapping honeycomb strips 23, which permit the passage of cooling air between said outer and inner cylindrical shroud walls 20 and 18, respectively. There is likewise free passage for cooling air between the outer side of the combustion chamber 2, the variable discharge nozzle 6 and the aft shroud portion 21.

Referring to Figs. 1 and 7, the shroud 19 is mounted for longitudinal movement with reference to the afterburner combustion chamber 2, which movement is accomplished in the following manner. Secured to the outer surface of the cylindrical outer shroud wall 2G are four equally spaced longitudinal brackets 24 having rod-end-mounting channels 25 spot-Welded thereto. Secured by a connecting bolt 26 to each longitudinal bracket 24 is the rod end 27 of a hydraulic linear actuator 28 which is arranged parallel to the longtudinal axis of the afterburner and is mounted by means of an actuator bracket 29 to the afterburner support ring 1. Hydraulic fluid is supplied to the linear actuators 23 under pressure from a source not shown by means of hydraulic lines 30, which are arranged in parallel circuit for simultaneous extension and retraction of the actuator 28. It is to be noted that, as mounted on the afterburner support ring 1, the linear actuators 28 are held in tension by the exhaust gases which pass through the shroud 19 which transmit the load to the movable shroud by means of extender elements 36 and connecting linkage; hence, the brackets 29 need be neither heavy nor cumbersome.

Referring now to Figs. 2, 3, and 5, there are spotwelded in longitudinal alignment along the inner surface of the streamlined converging aft portion 21 of the shroud 19, a plurality of pairs of forward and aft roller brackets 31, 32, comprising bracket angles mounted back-toback and having transverse bores 33 through which are secured roller pins 34, mounting on each side of the roller brackets 31, 32, the rollers 35. ver these rollers 35 are slid on longitudinally endwise, the shroud extender elements or flaps 36, which may be described generally as hat-sections necked inwardly adjacent their flanges 37, 37', to form a guideway 38 having an opening slightly wider than the thickness of the roller brackets 31, 32. The guideway 38 communicates with a raceway portion 39, which is nearly square in section and is adapted for rolling engagement and enclosure of the rollers 35. These shroud extender elements or aps 36 are disposed longitudinally adjacent each other, with the anges 37 joggled, as at 40, to closely overlay the flange 37 of the neighboring shroud extender element 36. It is apparent from Figs. 1 and 5 that when the vshroud extender elements 36 are moved relative to their supports, as in Fig. 1, there will be a substantial amount of convergence of the adjacent elements; and the width of the joggled portion 40 is suiciently great to permit such convergence.

Referring to Fig. 4, there is illustrated a fragmentary rear end View, showing along the upper edge thereof, the overlapping annulus of T-shaped nozzle segments 8 and slightly below center thereof the overlapping shroud extender anges 37, 37', and joggled extensions 40. It will be seen that the under or outer portions of said anges present an unbroken streamlined surface, save only for the narrow guideways 38 and the lines of the joggled portions 40. Inasmuch as both the guideway 38 and the joggled portions 40 extend longitudinally, this presents no aerodynamic problem; and since both are substantially sealed, performance is not impaired.

Spot-welded to the outer side of the raceway portion 39 of each shroud extender element 36 is a pair of nozzle segment connector plates 41, which may be generally triangular in shape with their apices extending inwardly. Adjacent the apices are lateral bores 42 through which pivot pins 43 are laterally passed and secured, as in Fig. 5.

In order to secure the shroud extender elements 36 over the rollers 35 and limit their travel, each is provided With a lateral removable pin such as a clevis stop pin 44, shown in Fig. 6 as being located across the midpoint of the raceway 39 and passing through the nozzle segment connector plates 41, which add bearing strength.

ln order to insure against leakage of the exhaust gases between the nozzle segments 8, should the provision of the overlapping portions 10 be deemed insufficient for this purpose, spring steel seals may be utilized by attachment to the nozzle segments 8 between the stem portions 11, shown in Fig. 5. There have been several types of such spring steel seals developed, and they are well known in the art of variable diameter exit nozzles and hence do not constitute a part of the present invention.

The manner of operation of the present invention may now be described. When the afterburner is being operated, the shroud 19 is moved towards its aft position, as shown in full lines in Fig. l, in which case the shroud extender elements or ilaps 36 will be substantially within the converging aft shroud portion 21, as shown in Fig. 2. In the fully aft shroud position each clevis pin 44 will bear against the aft side of the rollers 35 mounted on the forward roller brackets 31. Inasmuch as the forward roller brackets 31 are spaced radially outward from the hinge ring 7 a fairly substantial distance, the nozzle segments 8 will be diverged as shown in Fig. 2. Such radial distance may be noted from the postion of the ray designated a in Fig. 2.

In contrast, when the shrud 19 is moved forward for non-afterburning operation, as in Fig. 3, the shroud extender elements 36 are detained in their aft position by the pivot pins 43 and assume the position shown in Fig. 3 with the clevis stop pins 44 abutting the forward side of the rollers 35 mounted on the aft roller brackets 32. In this position the approximate midpoint of each shroud extender element 36 is inward as far as the att roller brackets 32, indicated by the ray designated b. Hence, forward movement of the shroud 19 is accompanied by convergence of the nozzle segments 8 and the shroud extender elements 36 will assume the converged position shown in phantom lines in Fig. 1.

It is to be noted that the linear actuators 28 and the supporting and connecting members therefor are the only elements of mechanism which are external to the shroud 19. These are so arranged as to be readily fitted within the aft portions of the engine nacelle cowling 45, as shown in Fig. 1. The streamlined converging aft shroud portion 21 forms a continuation of the nacelle 45 as a streamlined afterbody therefor, being perfectly faired to the lines of said nacelle 45 during non-afterburning operation and departing only slightly from true streamlined form in the afterburning position as shown in Fig. 1.

Cooling air ducted along the outside of the throat portion 3 of the afterburner by the nacelle 4S will be caused to flow between the shroud 19 and the cylindrical portion of the afterburner combusion chamber, and thence along the outside of the exit portion 5 of the afterburner chamber tobe exhausted between the T-shaped nozzle segments 8 and the shroud extender elements 36. It is to be noted that a relatively smooth annular exit port, extending beyond the annulus of nozzle segments 8, is provided for the cooling air regardless of whether the shroud is in afterburning or non-afterburning position. Inasmuch as the engine exhaust gases are emitted from the nozzle segments 8 at high velocity, in either position there will be augmentation of the flow of the cooling air, varying in part as a function of the velocity of the exhaust gases. Hence, both in afterburning and in nonafterburning operation there cooling effect.

In the embodiment illustrated, the convergence of the shroud extender elements 36 on the forward movement of the shroud 19 is not quite as great as-the convergence of the nozzle segments 8; but this could be arranged by detail design if desired. In any event, the base drag, as heretofore defined, will be substantially minimized; whereas with the use of a conventional fixed shroud having an aft end opening large enough to clear the blast cone from an enlarged nozzle during afterburning, the base drag during non-afterburning operation will be seriously large.

The shroud extender elements or shroud flaps are entirely novel. Reference to Fig. 2 discloses that the extender elements 36 are not at along their flanges 37, but are curved along a radius conforming substantially with the curvature of the aft end of the streamlined converging aft portion 21 of the shroud 19. Thus, on forward movement of the shroud 19, the shroud extender elements 36 move not merely inward but convergingly inward radially toward the longitudinal axis of the engine.

From a mechanical standpoint, the operation ofthe present variable shroud is simple, positive, and highly reliable. The lateral pivot pins 43 which connect the nozzle segments 8 to the shroud extender elements 36 serve in effect to detain them from forward and aft movement with the shroud 19; and the aligned forward and aft roller brackets 31, 32, and the rollers 35 thereon serve, along with the guideways 38 and raceways 39, to key the shroud extender elements 36 for detention against longitudinal movement with the shroud 19. All of the moving parts are adequately cooled. The manufacturing processes are simple, because the shroud extender will be a suitable ejector elements 36 are roll-formed. Assembly and dis-assembly is quick and simple.

It is to be further noted that the components employed are a large number of identical parts. For example, each of the nozzle segments 8 is identical with each other nozzle segment and the same applies to the shroud extender elements 36, the connector plates 41, and the forward and aft roller brackets 31, 32. It is important that these roller brackets be aligned accurately in foreand-aft relationship and also with regard to their longitudinal position, that is, all the forward brackets 31 should be at the same longitudinal station so that the clevis stop pins 44 will engage them simultaneously, as shown in Fig. 2. Save for the locating of the roller brackets 31, 32, the assembling of the components requires no precise positioning and parts are readily interchangeable.

The number of linear actuators 28 employed is a matter of choice. In practice, four have been found suicient and these may be of sufficiently small diameter to be accommodated readily within the nacelle 45.

It should be understood that changes and modifications in the form, construction, arrangement and combination of the several parts of the invention may be made and substituted for those herein shown and described without departing from the nature and principles of the present invention.

What I claim is:

1. In a jet engine afterburner having an aft-extending tubular combustion chamber, the combination comprising a variable diameter exit nozzle of the pivoted multiple-segment type, a cooling shroud surrounding and `spaced. outward from said chamber and nozzle, said shroud having a converging aft portion and an aft end opening of greater diameter than the greatest diameter of the aft edge of said exit nozzle, a plurality of shroud exit aps corresponding radially with said nozzle segments and mounted for relative fore-and-aft movement with respect to the inner surface of said converging aft portion, aligned pin connections between each shroud exit flap and the corresponding nozzle segment, said pin connections positioning the aft ends of said shroud exit ilaps aft of said nozzle segments and outwardly thereof for clearance of blast gases; and a fore-and-aft actuator secured to said shroud and so constructed and arranged that forward movement of said converging aft portion forward of the rear end of said shroud exit aps converges both said shroud exit aps and said nozzle segments.

2. In a jet engine afterburner having an aft-extending tubular combustion chamber, the combination comprising a variable exit jet nozzle, a cooling-air ducting shroud surrounding said chamber and nozzle and supported for longitudinal movement relative thereto, said shroud being in the form of a streamlined afterbody converging to and terminating in an aft end opening of greater diameter than the greatest diameter of the aft edge of said exit nozzle, a plurality of overlapping shroud extender elements mounted side-by-side and adapted for relative foreand-aft movement with respect .to the inner surface of said aft end opening so as to, in one position of said shroud extend convergingly through said aft end opening, mechanism connected between said extender elements and said variable exit jet nozzle and being adapted for relating the converging movement of said shroud eX- tender elements with the diminution of said exit nozzle and for relating the diverging movement thereof with the enlargement of said nozzle, said mechanism detaining said shroud extender elements from longitudinal movement with said shroud; and a fore-and-aft actuator linking said shroud to the structure of said engine.

3. In a jet engine afterburner, the combination comprising an exit nozzle hinge ring, exit nozzle segments hinged thereto for convergence and divergence simultaneous with each other to vary the cross-sectional area of the exit nozzle, a pin connection on the outer side of each nozzle segment spaced from said hinge ring, a shroud in the form of a hollow streamlined afterbody converging to and terminating in an aft end opening, support structure between said shroud and the engine adapted to permit longitudinal positioning of said shroud relative to the engine in any position between a forward, or nonburning, position and in an aft, or afterburning, position, a plurality of parallel linear actuators secured between said shroud and engine for selecting and retaining such positions, a plurality of adjacent shroud extender elements mounted along the aft inner surface of said streamlined afterbody for converging movement upon forward displacement of said shroud, and for expanding movement upon aft displacement of said shroud, and a pivot pin bracket secured to each shroud extender element for attachment to the pin connection of a radially corresponding exit nozzle segment, so constructed and arranged that on forward movement of said shroud the converging shroud extender elements urge the exit nozzle segments inward and attain an exposed position partly outward from the aft opening of said shroud in the formation of a reduced end opening therefor.

4. In a jet engine afterburner having an aft-extending tubular combustion chamber, the combination comprising a variable diameter exit nozzle of the multiple segment type, a cooling shroud surrounding and spaced outward from said chamber and nozzle and supported for longitudinal movement relative thereto, said shroud having a converging aft portion and an aft end opening of greater diameter than the greatest diameter of the edge of said exit nozzle, a plurality of shroud exit flaps-carried by said shroud and adapted for longitudinal sliding movement relative to and along the inner surface of said converging aft portion, motion transmitting means connected between said shroud exit aps and said exit nozzle segments, said motion transmitting means relating outward movement of said aps with the enlargement of said.

nozzle and inward movement with the diminution thereof, longitudinal movement of said shroud positioning the aft ends of said shroud exit flaps aft of said nozzle segments and outwardly thereof for clearance of blast gases; and fore-and-aft actuator means connected with said shroud and said combustion chamber whereby aft movement of said shroud effects the radially outward movement and covering of said shroud exit flaps and opens the exit nozzle to afterburning position, and forward movement of said shroud eiects the radially inward movement of said shroud flaps, bares the aft portions thereof to serve as nacelle ends, and reduces the exit nozzle diameter to non-afterburning position.

5. In a jet engine afterburner having an aft-extending tubular combustion chamber, the combination comprising a variable diameter exit nozzle of the multiple-segment type, a cooling shroud surrounding and spaced outward from said chamber and nozzle and supported for longitudinal movement relative thereto, said shroud having a converging aft portion with concave inner surface and an aft end opening of greater diameter than the greatest diameter of the aft edge of said exit nozzle, a plurality of shroud exit flaps carried by said shroud for longitudinal sliding movement relative to and along the said concave inner surface of said converging aft portion, motion transmitting means connected between said shroud exit flaps and said exit nozzle segments, said motion transmitting means relating outward movement of said aps with the enlargement of said nozzle and inward movement with the diminution thereof, longitudinal movement of said shroud positioning the aft ends of said shroud exit aps aft of said nozzle segments and outwardly thereof for clearance of blast gases; and fore-and-aft actuator means connected to said shroud and to said combustion chamber, whereby aft movement of said shroud effects the radially outward and diverging movement and covering of said shroud exit flaps and opens the exit nozzle to afterburning position, and forward movement of said shroud effects the radially inward and converging movement of said aps, bares the aft portions thereof to serve as nacelle ends and reduces the exit nozzle diameter to non-afterburning position.

6. In a jet engine afterburner having a combustion chamber exit portion, the combination of an adjustable shroud longitudinally movable relative to the combustion chamber exit portion between extended `and retracted positions havingvminimum base drag respectively corresponding with afterburner operation and non-afterburner operation, and means for varying the discharge diameter of the exit portion in accordance with the blast cone for afterburner operation and non-afterburner operation respectively, said means including a plurality of nozzle segments movably carried by the combustion chamber exit portion within said shroud in both of its positions and a plurality of flap elements movably connected between said nozzle segments and said shroud for transmitting movement to said nozzle segments upon shroud movement.

7. ln a shrouded exhaust nozzle for jet engine afterburners having a combustion chamber body terminating in an exit portion, the combination of a plurality of nozzle segments pivotally connected with said exit portion for converging and diverging displacement to vary the final discharge opening of said exit portion, a shroud longitudinally movable relative to the combustion chamber and extending aft to enclose said nozzle segments, power means on the jet engine connected to said shroud and adapted to move the latter longitudinally to displace said nozzle segments, and means operatively connected between said nozzle segments and shroud including a plurality of flap elements pivotally connected to said nozzle segments and roller means connecting said shroud and ap elements to permit relative movement between said shroud and ilrap elements.

References Cited in the le of this patent UNITED STATES PATENTS 

